1. Field of the Invention
This invention relates in general to improvements in the lubrication systems of earth penetrating tools.
2. Description of the Prior Art
Earth penetrating tools, including the rotatable cutter type earth boring drill bit, commonly utilize bearing lubrication systems. The successful lubrication of drill bit bearings was made practicable with the development of a seal capable of operating in the detrimental environment and conditions associated with earth boring. One of the most commercially successful seals is described in the U.S. Pat. to Atkinson, et al., No. 3,075,781. Improvements to such seals are disclosed in the U.S. Pats. to Cunningham, et al., Nos. 3,137,508 and 3,119,878; and to Farr, et al., No. 3,313,552. The O-ring type seal has been successfully used in earth boring drill bits as described by Galle in U.S. Pat. No. 3,397,928.
A successful lubrication system for an earth boring drill bit generally includes in addition to a successful seal a compensator system that limits the pressure differential across the seal. One such compensator may be seen for example in the U.S. Pat. to Eenick, No. 3,007,751, and others in the U.S. Pats. to Cunningham, Nos. 3,007,750 and 3,137,508.
In addition to a successful compensator system, it is advantageous to include a pressure relief valve to relieve the lubrication system from excessive pressures caused by thermally induced expansion, or by the creation of gaseous hydrocarbons or other phenomenon. A successful pressure relief valve is disclosed in the U.S. Pat. to Galle, No. 3,476,195. While the pressure relief valve in this patent operates successfully in most instances, it has the disadvantages that foreign matter sometimes enters the valve region and by jamming its components prevents successful operation.